Since QTopia SDK 1.7 only supports Zaurus SL-5500, but not support PDAs using XScale CPU such as SL-5600, SL-6000, SL-C860 and so on. I want to write programs for SL-C860, therefore I want to know where can I find QTopia SDK which supports XScale CPU. Can you tell me?

. qtopia 1.7 snapshot
. qt-embedded (2.3.7 or 2.3.8 snapshot)
. qt-2.3.2 if you want to test your application first on PC.
. a cross-compiler. The one you want. The one that will support XScale CPU like the one on handhelds.org.

The compiler setup section is probably the one you want to start off with.
There are also plenty of existing discussions on this website about setting up a development environment, and the problems you may encounter.

The sl 5500 has a StrongArm processor which uses the ARM4 instruction set.

The C machines (and sl5600) have Intel XScale processors which use the ARM5 instruction set.

ARM instruction sets are backward compatible. Therefore you can run (and program) for a 5500 and it'll work on a C machine, but not vice-versa (which is why the majority of programs compiled for the pdaXrom won't work on my 5500).

So the answer is that what's available will work, but won't be optimised (ie using the latest ARM5 instruction set - though I'm not sure what kind of speed/size differences this produces in any case). If you want it optimised you'll have to roll your own.

If you want to roll your own, then the easiest thing to do is probably to look at the pdaXrom SDK which builds (from source) libc 2.2.x and GCC 3.x with xscale optimisations (or the OZ OE system for that matter). Take a look at the makefiles (or I can provide them if you can't be bothered to download it all yourself).

Actually even easier would be to just use the pdaXrom cross-toolchain (which has xscale optimisations enabled). I imagine this will work without troubles after you copy across the Qtopia base libs, etc.

Do you really need the xscale optimisations though? What kind of stuff are you thinking of building? I'd recommend that you just use the standard Sharp cross-toolchain until you become familiar with it all then possibly make your own toolchain if you need it.

lardman's question about whether you really need the Xscale optimizations is a valid question that any developer should consider. It depends on what you are attempting to do with your software.

I've had a comparison between GCC optimizations on my zaurus web page for quite some time. I added another page last night which compares the SL-5600 standard and overclocked kernels with the SL-6000. The comparisons use nBench and can be found here. You should look at the nbench-armv4, nbench-armv5te, nbench-cpu-xscale and nbench-tune-xscale tables. The results vary, but xscale opimizations usually are the best.

I guess I should mention on my web page that my SL-5600 has the PXA-250, since there are some SL-5600s with the PXA-255.